Embodiments of the inventive concept relate generally to semiconductor memory devices, and more particularly to nonvolatile memory devices, read methods for the nonvolatile memory devices, and memory systems incorporating the nonvolatile memory devices.
Semiconductor memory devices can be roughly divided into two categories according to whether they retain stored data when disconnected from power. These categories include volatile memory devices, which lose stored data when disconnected from power, and nonvolatile memory devices, which retain stored data when disconnected from power. Examples of volatile memory devices include dynamic random access memory (DRAM) and static random access memory (SRAM). Examples of nonvolatile memory devices include read only memory (ROM), programmable read only memory (PROM), electrically programmable read only memory (EPROM), electrically erasable and programmable read only memory (EEPROM), flash memory, phase-change random access memory (PRAM), magnetic random access memory (MRAM), resistive random access memory (RRAM), and ferroelectric random access memory (FRAM).
Flash memory device is an especially popular type of nonvolatile memory device due to attractive features such as relatively high storage capacity, low power consumption, and the ability to withstand physical shock. In view of this continuing popularity, researchers are constantly pursuing ways to improve flash memory devices. For example, researchers are continually pursuing ways to improve the speed and accuracy of read and write operations as well as storage capacity.